Hypoglycemic activity of the antioxidant saponarin, characterized as α-glucosidase inhibitor present in Tinospora cordifolia

Figures & data

Figure 1.  α-glucosidase inhibitors.

Table I.  Saponarin content of Tinospora cordifolia leaves.

T.cordifolia leaves	Saponarin (mg /gm dried aqueous extract)
Newly emerged leaves	45.5 ± 3.5
Mature green leaves	36.2 ± 2.1
Yellow old leaves	32.1 ± 1.5

Methods for the estimation of saponarin have been described in the text. Results represent mean data obtained from three sets of experiments with one set of leaves collected at a time from one plant. On average, 60–65 gm of fresh leave yielded 1 gm of dry solid in aqueous extract and 400 mg in acidic methanolic extract according to protocol used in the study.

Figure 2.  Hydroxyl radical scavenging capacity of dried aqueous extract of Tinospora cordifolia leaves. Methods for preparation of dried leaf extract and determination of hydroxyl radical scavenging activity were as described in text.

Figure 3.  Determination of Ki of saponarin on maltase and sucrase. Dixon plot (1/V vs I) for inhibition of saponarin on activities of intestinal maltase (a), intestinal sucrase (b), fungal maltase (c) and fungal sucrase (d). Saponarin (10–80 μM) was added against different concentrations (0.5–4 mM) of maltose [S]. Enzyme activities were assayed by the method as described in text.

Figure 4.  Determination of ki′ of saponarin on maltase and sucrase. S/V vs I plot for inhibition of saponarin on activities of intestinal maltase (a), intestinal sucrase (b), fungal maltase (c) and fungal sucrase (d). Saponarin (10–80 μM) was added against different concentrations (0.5–4 mM) of maltose [S]. Enzyme activities were assayed by the method as described in text.

Table II.  Saponarin inhibitor constant (μM) for maltases and sucrases of different origins.

Enzymes	IC50	Ki	Ki′
Maltase (Rat intestine)	48 ± 3.55	8 ± 0.15	19.5 ± 0.20
Sucrase (Rat intestine)	35 ± 1.95	6 ± 1.33	13 ± 0.13
Maltase (Aspergillus niger)	55 ± 3.53	9 ± 0.085	27 ± 0.195
Invertase (Baker's yeast)	48 ± 1.32	8 ± 0.072	20 ± 0.089

Values were determined from Dixon plots (Figure 3) and S/V vs I plot (Figure 4). Mean values presented were obtained from three similar sets of data obtained separately.

Figure 5.  Hypoglycemic activity of saponarin. Saponarin (20–80 mg/kg body weight) was orally administered to the SD rats. Five minutes later, maltose (2 gm/kg body weight) was fed orally to the rats and the effect on blood glucose was recorded till 120 min. Controls were fed orally with equal volume of physiological normal saline. Results presented were mean values obtained from three sets of identical experiments. -▪- Control; -△- 20 mg/kg; -▴- 40 mg/kg; -•- 80 mg/kg.